My copending application Ser. No. 608,885, filed Aug. 29, 1975, and my subsequent copending application Ser. No. 686,585 filed May 14, 1976, disclose an improved energy absorber, particularly an adjustable hydraulic shock absorber, which has proven highly desirable with respect to both its energy absorbing capability and its adjustability. This shock absorber has also proven desirable since the internal flow control structure permits the absorption of energy as imposed on the external ram without resulting in excessive heating of the fluid, which phenomena is commonly encountered in other known shock absorbers employing alignable flow control openings. Further, the shock absorber disclosed in my copending applications has exhibited superior wear characteristics in that the flow control sleeves have experienced substantially less erosion-type wear, particularly around the flow openings, than was commonly experienced in prior shock absorbers.
The shock absorber disclosed in the above-mentioned applications have also exhibited highly desirable durability and strength, while at the same time greatly facilitating the manufacture and assembly of the shock absorber by permitting easier selection of parts, and minimizing the problems of alignment during assembly of the shock absorber.
While the shock absorber disclosed in the above-mentioned application possesses highly desirable and superior structural and operational characteristics, particularly in contrast to prior shock absorbers employing alignable flow control openings, nevertheless there still exists the need for a durable and efficient shock absorber which will automatically self-adjust during operation so as to compensate for variations in the applied load.
One prior attempt at providing such an automatically self-adjusting shock absorber is disclosed in U.S. Pat. No. 3,750,856, issued to Kenworthy. The shock absorber of this patent, however, utilizes concentric inner and outer control sleeves having a plurality of openings formed therein, which openings are alignable to control the flow between inner and outer chambers. The use of such alignable openings is undesirable since, as noted above, structures of this type experience substantial wear due to erosion around the openings. The fluid also experiences undesirable heating. In addition, the automatic adjustment in this shock absorber is achieved by utilizing the increased pressure within the piston-receiving chamber to activate one of the sleeves for displacing same axially, thereby decreasing the overlap between the aligned openings so that the fluid flow between the chambers is further restricted. This mode of operation thus results in increased throttling of the fluid between the chambers, which thereby increases the erosion around the openings and also the heating of the fluid. Further, if the shock absorber is not properly initially adjusted with respect to the stop which coacts with and limits the axial displacement of the movable control sleeve, then the sudden application of a large shock load can cause a "lock up" of the shock absorber due to the pressure fluid causing a complete closing off of the openings. Thus, this shock absorber possesses numerous undesirable features and does not provide for automatic self-adjustment of the shock absorber in a manner which results in optimum flow control.
Another variation of a known automatically adjustable shock absorber is disclosed in U.S. Pat. No. 3,605,960, issued to Singer. The shock absorber of this patent, however, possesses the same basic structure as Kenworthy, described above, and thus possesses the same disadvantages.
Accordingly, it is an object of the present invention to provide an improved shock absorber which automatically self-adjusts when a load is imposed thereon so as to result in optimum absorption of energy, which shock absorber overcomes the above-mentioned shortcomings.
A further object of this invention is to provide an improved self-adjusting shock absorber, as aforesaid, which possesses a flow control structure wherein the dimension of a flow passage automatically increases in response to pressure increases within the shock absorber, thereby permitting at least momentary increased flow to minimize the fluid pressure, whereby the optimum energy absorption characteristic of the shock absorber is accordingly automatically adjusted in response to the characteristics (such as force, velocity and acceleration) of the applied load.
Other objects and purposes of this invention will be apparent to persons familiar with shock absorbers upon reading the following specification and inspecting the accompanying drawings.
To summarize the present invention, the shock absorber includes a housing having a ram slidably extending therefrom. A pair of concentric control sleeves divide the housing into innner and outer fluid chambers. A piston associated with the ram is slidably received within the inner chamber. The inner control sleeve has an axially aligned row of openings therein, and also has an elongated groove formed in the outer periphery thereof, which groove is circumferentially spaced a preselected distance from the row of openings. The outer sleeve is preferably free of openings. The inner and outer sleeves have compatible outer and inner conical surfaces, respectively, adapted to form a narrow clearance space therebetween. A spring coacts between the housing and the outer sleeve for urging same axially in a direction whereby the openings in the inner sleeve are effectively closed, as by maintaining the narrow space between the conical surfaces to a minimum dimension. When a shock load is imposed on the ram causing the piston to move inwardly within the inner chamber, the fluid within the inner chamber is pressurized and flows outwardly through the openings into the narrow space. The pressure of the fluid as it reacts against the conical surface on the outer sleeve causes the outer sleeve to be axially displaced in opposition to the urging of the spring, thereby increasing the dimension of the narrow space whereby the fluid flows therethrough into the adjacent groove, from which it is discharged into the outer chamber. The spring thus causes the outer sleeve to automatically axially adjust responsive to the pressure of the fluid so as to provide the optimum dimension of the narrow space between the sleeves, thereby resulting in optimum absorption of the energy from the externally applied load.